No abstract

The purpose of this paper is to develop a network coding scheme to enhance TCP performance in wireless sensor networks. It is well known that TCP performs poorly over wireless links which suffer from packet losses mainly due to the bad channel. To address this problem, it is useful to incorporate network coding into TCP, as network coding can offer significant benefits in terms of throughput, reliability, and robustness. However, the encoding and decoding operations of network coding techniques will bring an additional delay that has a negative effect on applications of wireless sensor networks. In this paper, we propose an adaptive network coding (ANC) scheme which contains two major aspects: the adjustment of the redundancy factor R and the adjustment of the coding window size CW . We dynamically adjust these two parameters depending on the measured packet loss rate, so that the proposed ANC can effectively mask packet losses and reduce the decoding delay of network coding. The performance of our scheme is evaluated by simulations using NS-2 simulator. Compared to other schemes, the ANC not only achieves a good throughput but also has the lowest average delay and the lowest maximum delay in all experimental environments.

No abstract

A critical design issue of Transmission Control Protocol (TCP) is its congestion control that allows the protocol to adjust the endto-end communication rate based on the detection of packet loss. However, TCP congestion control may function poorly during its slow start and congestion avoidance phases. This is because TCP sends bursts of packets with the fast window increase and the ACK-clock based transmission in slow start, and respond slowly with large congestion windows especially in high bandwidth-delay product (BDP) networks during congestion avoidance. In this article, we propose an improved version of TCP, TCP-Ho, that uses an efficient congestion window control algorithm for a TCP source. According to the estimated available bandwidth and measured round-trip times (RTTs), the proposed algorithm adjusts the congestion window size with a rate between exponential growth and linear growth intelligently. Our extensive simulation results show that TCP-Ho significantly improves the performance of connections as well as remaining fair and stable when the BDP increases. Furthermore, it is feasible to implement because only sending part needs to be modified.

No abstract